Method of making containers for fluids under pressure



Feb. 14, LANSKY ETAL METHOD OF MAKING CONTAINERS FOR FLUIDS UNDER PRESSURE Original Filed Oct. 16, 1963 a k 20 v Fly. 2 e an 7 22 23 INVENTORS 25 ZDENEK J. LANSKY KURT w. n. LEIBFRITZ ATTORNEY United States Patent Oflfrce 3,303,560 Patented Feb. 14, 1967 3,303,560 METHOD OF MAKING CONTAINERS FOR FLUIDS UNDER PRESSURE Zdenek J. Lansky, Winnetka, and Kurt W. H. Leibfritz,

Norridge, 111., assignors to Parker-Hannifin Corporation, Cleveland, Ghio, a corporation of Ghio Original application Oct. 16, 1963, Ser. No. 316,739, now Patent No. 3,241,700, dated Mar. 22, 1966. Divided and this application Oct. 23. 1965, et. No. 503,446 3 Claims. (Cl. 29-421) This application is a division of co-pending application Serial Number 316,739, filed October 16, 1963, now Patent 3,241,700, dated March 22, 1966.

This invention relates to the method of making containers for fluids under pressure and more particularly to the method of reinforcing transparent bowls for lubricators and filters for use in pneumatic power systems.

In airline lubricators of the general type disclosed in Patent 2,889,009, a liquid lubricant is contained within a transparent bowl which is attached to a body member having connection to a pipe line for delivering air under pressure to a pneumatically operated device. The liquid lubricant is exposed to the air under pressure whereby it is forced through a pick-up tube extending into the bowl and through passages in the body so as to enter the air stream passing through the body in atomized form for lubricating the device being operated. With this arrangement, the bowl containing the lubricant is exposed to the full operating pressure of the system. Since it is desirable to have the bowl of transparent material so that the level of the lubricant is readily visible, it is a common practice to make the bowl of glass or a plastic. However, glass and some of the plastics are fragile and break when accidently struck with an object, or they burst due to excessive internal pressure. Such breakage or bursting of glass or fragile plastics can be dangerous to persons because of flying particles and may also cause shut down of the pneumatic system until the bowl has been replaced.

In recent years, shatter-proof transparent plastics, such as polycarbonates, have come into use for bowls on lubricators of this type. These plastics have sufficient ductility to prevent shattering under impact and ordinarily do not shatter when they burst due to excessive internal pressures. However, these ductile plastics are subject to attack by certain chemicals which may be the base or an additive in the lubricant, as for example, detergent in detergent oils, carbon tetrachloride, and phosphate esters, which chemicals cause tensile stresses to build up within the plastic material. When the bowls are thus subjected to tensile stresses because of chemical attack, their ability to withstand bursting due to internal fluid pressure is greatly reduced and moreover the ductility is impaired so that bursting will cause the bowl to shatter into sharp fragments and thus endanger personnel.

To overcome the effects of chemical attack upon bowls of polycarbonate and like ductile plastics, applicant has devised a perforated metallic shield and a method of applying the same to the bowl so that the bowl is placed under compressive stresses for counteracting tensile stresses resulting from chemical attack and for interlocking the shield and bowl to prevent inadvertent separation thereof.

It is thus an object of the method of the present invention to provide a transparent bowl of polycarbonate or other ductile plastic with a perforated metal shield which permits the interior of the bowl to be viewed and which prestresses the bowl to prevent weakening by chemical attack.

It is another object to provide a method of attaching a perforated metallic shield to a bowl of ductile plastic whereby the bowl is placed under compressive stress and interlocked with the shield to prevent separation.

Other objects of the invention will be apparent from the following description and from the drawings in which:

FIG. 1 is a view, partly in cross section, of a lubricator with a perforated metal shield contracted upon a ductile plastic bowl, and

FIG. 2 is a cross section view of the bowl and shield within a magnetic forming device before contraction of vthe shield upon the bowl.

An airline lubricator fitted with a plastic bowl in accordance with this invention may include a body member 10 connected to an air supply line 11 and an air delivery line 12 and having a bowl 13 of transparent ductile plastic attached thereto and containing a liquid lubricant 14. The body 10 has passages, not shown, for directing air under pressure from supply line 11 into the interior of the bowl for pressurizing lubricant 14 to force the latter upwardly through pick-up tube 15 to other passages (not shown) for causing it to enter the air in delivery line 12 in atomized form.

A cylindrical metal shield 16 having a plurality of circular perforations 17 is assembled upon the plastic bowl 13 in a manner to impose compressive stresses upon the latter and so that portions of the plastic bowl project into the perforations 17 to lock the bowl and shield against accidental separation.

As shown in FIG. 2, bowl 13 is initially formed with a cylindrical wall 20 having a smooth outer surface 21. The metallic shield 16 is initially formed in cylindrical shape with an inner diameter that is a close fit over the outer diameter of bowl wall 20 and is preferably no smaller than such diameter. After the metal shield has been slipped over the plastic bowl as shown in FIG. 2, the parts may be placed within a magnetic forming device indicated at 22 and the latter operated for imposing magnetic force upon shield 21 for contracting the latter in diameter. This magnetic force does not act upon bowl 13.

The metal shield 16, when contracted by the magnetic force, causes contraction of the plastic bowl in the areas between perforations 17 and thus imposes considerable compressive stress on the material of the plastic bowl in these areas. Meanwhile, the plastic material 23 which is opposite each perforation 17 remains substantially at its original diameter or location and thus enters the per-foration as the shield is contracted. This effectively interlocks the shield and bowl to prevent displacement of the one from the other.

The magnetic force also causes contraction of the lower end 25 of the metal shield so that it intimately engages the curved lower end of the plastic bowl, as indicated in FIG. 1.

The upper end of bowl 13 has a flange 25 whose lower face 26 is engageable by a clamp nut 27 for clamping the bowl against the lower end of body 10 with a resilient packing ring 28 providing a seal therebetween.

With shield 16 contracted upon bowl 13 as described, the shield protects the bowl against breakage from being struck by external objects. Also, the bowl is under compressive stress which compensates for tensile stresses im posed upon the bowl material by action of chemicals contained within lubricant 14, and thus the bowl is further able to resist bursting due to internal fluid pressure.

By placing the plastic bowl under an initial compressive stress it is also possible to used a thinner wall thickness than otherwise. Thus, as the bowl is pressurized its wall section goes from compression to a balanced stress and then into tension, with the ultimate tension stress being much lower than if the bowl had not been placed under initial compression.

We claim:

1. The method of making a receptacle comprising forming'a hollow cylindrical container from a material capable of appreciable plastic deformation without fracturing, forming a perforated cylindrical shield with an inside diameter substantially the same as the outside diameter of the cylindrical container, assembling the shield over the cylindrical container and contracting the shield to a lesser inside diameter than the initial outside diameter of the container while the inside diameter of the container is unsupported whereby the container is contracted in inside and outside diameter between said perforations so as to place the container material between the perforations in' compressive stress and the container material opposite the perforations remains substantially non-contracted so as to extend into the perforations for locking the shield upon said container.

2. The method of claim 1 in which the shield is metallic and is contracted by magnetic force and the container is of plastic material that is impervious to magnetic force.

3. The method of claim 2 in which the container is of polycarbonate plastic material.

References Cited by the Examiner UNITED STATES PATENTS 1,067,991 7/1913 Kroger 29523 2,828,537 4/1958 Pischke et a1. 29-517 2,976,907 3/1961 Harvey et a1.

2,978,263 4/ 1961 Walsh et a1 29508 X 3,160,428 12/1964 Goodall 285-256 3,239,930 3/1966 Violleau 29516 CHARLIE T. MOON, Primary Examiner 

1. THE METHOD OF MAKING A RECEPTACLE COMPRISING FORMING A HOLLOW CYLINDRICAL CONTAINER FROM A MATERIAL CAPABLE OF APPRECIABLE PLASTIC DEFORMATION WITHOUT FRACTURING, FORMING A PERFORATED CYLINDRICAL SHIELD WITH AN INSIDE DIAMETER SUBSTANTIALLY THE SAME AS THE OUTSIDE DIAMETER OF THE CYLINDRICAL CONTAINER, ASSEMBLING THE SHIELD OVER THE CYLINDRICAL CONTAINER AND CONTRACTING THE SHIELD TO A LESSER INSIDE DIAMETER THAN THE INITIAL OUTSIDE DIAMETER OF THE CONTAINER WHILE THE INSIDE DIAMETER OF THE CONTAINER IS UNSUPPORTED WHEREBY THE CONTAINER IS CONTRACTED IN INSIDE AND OUTSIDE DIAMETER BETWEEN SAID PERFORATIONS SO AS TO PLACE THE CONTAINER MATERIAL BETWEEN THE PERFORATIONS IN COMPRESSIVE STRESS AND THE CONTAINER MATERIAL OPPOSITE THE PERFORATIONS REMAINS SUBSTANTIALLY NON-CONTRACTED SO AS TO EXTEND INTO THE PERFORATIONS FOR LOCKING THE SHIELD UPON SAID CONTAINER. 